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Posts: 9
Joined: Fri Mar 03, 2017 8:34 pm

What is the Lower Calorific Value of biofuels (Waste Vegetable Oil)

Thu Mar 09, 2017 6:38 pm

Hey guys, I am currently trying to calculate how much power output biofuels produce compared to standard kerosene fuel. There have been commercial aircrafts that have been blending biofuels with kerosene 50/50 so I wanted to calculate if there is a reduction in power output from the engine or not.

The formula I am looking at is:
LCV = mair*Cp(T4-T3)/mf

mair=mass flow rate of air
mf = mass flow rate of fuel

Which shows that if there is a decrease in LCV then there is a decrease in T4-T3 (temperature across the combustor of a turbofan), which means T4 will decrease, which in turn leads to a fall in engine efficiency and overall work from the turbing - so power output will decrease if LCV decreases. This is if all other parameters remain constant.

So does anybody know where I can find the LCV of waste vegetable oil, since that is a common type of fuel airlines are starting to use now.

I know this question is a bit technical, it comes under my Aero-Propulsion module for university so if there is anything you are unclear of, please let me know.

Thanks in advanced.
Posts: 1911
Joined: Thu Jul 20, 2006 6:28 am

Re: What is the Lower Calorific Value of biofuels (Waste Vegetable Oil)

Thu Mar 09, 2017 7:08 pm

My understanding is that it would fall in to the normal bands of variation for jet fuel. Where I work we have significant amounts of waste veg oil and that goes for fuel processing and is made into diesel. Diesel is very similar to jet fuel but has a few more additives for lubrication. I believe the standards for car fuel (in the UK at least) is way stricter than for aviation fuels. Yes the aviation fuel is checked more often but low sulphur car diesel has a tighter spec.

Posts: 1
Joined: Thu Mar 09, 2017 10:10 pm

Re: What is the Lower Calorific Value of biofuels (Waste Vegetable Oil)

Thu Mar 09, 2017 10:20 pm

Jet A1 is actually kerosene (not diesel) with tighter specifications and few additives such as lubricity (correctly noted above), anti static, anti corrosion and a few others. The LCV of waste vegetable oil is not what you are after. They don't actually use that in the fuel, they use that as a source of hydrocarbons to make the fuel. What you need is the LCV of the end refined product. There are various ways of getting to a biofuel product, and I recommend you contact a leading producer such as Neste Finland, Novvi USA and others whom I cant think of. Good luck with the studies.
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Joined: Fri Jun 15, 2012 11:27 pm

Re: What is the Lower Calorific Value of biofuels (Waste Vegetable Oil)

Fri Mar 10, 2017 5:35 am

As Croweater mentioned, bio-jet manufacturers take the veg oil and do whatever is needed in order to make it comply with the spec for jet fuel, so by definition, bio-derived fuels are in the same bands as petro-jet.

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